what I recall:
I thought the differences were pretty well hashed out in the
Gbox review that Linuxman did.
In looking up the link for the above review, I see he also did a
review of the Vbox 2, a few years earlier.
I'll refer you to those two reviews and the links given above by others, but I do recall that -some- models of the Vbox were pretty unreliable.
Which ones, I don't recall.
But I think there were Vbox 1's, 2's, 3's, 4's, and 5's.
So, don't assume they are interchangeable.
But, after hashing out how the Gbox worked and talking to Linuxman during his evaluation, I was certainly impressed with the Gbox.
And I ordered one earlier this year.
The double-counts provided by using reed switch
opening and
closing, boosts the positioning resolution.
This can't hurt on BUDs running Ku.
I'd suspect it would help on small Ku dishes run by
"actuators" or "jacks", as well as H-H BUD-movers like the AJAK series.
As discussed elsewhere, if you have sloppy mechanics the Gbox can't work miracles, of course.

But, there are a lot of BUD mounts 'n motors that are quite tight, and for them, and especially for Ku, the Gbox is unsurpassed.